During oil-well production, in-line pumps such as progressive cavity pumps are used to pump oil from the well bore to the surface. A progressive cavity pump system includes a surface driven rotor mounted within a downhole stator that is rotationally secured to production casing so as to prevent rotation of the stator in response to the rotation of the rotor. The stator is secured to the production tubing by a torque anchor that permits the stator to be positioned in the well at a desired location wherein upon clockwise rotation of the tubing string and connected tool string, the torque anchor will lock against the wellbore casing and thereby secure the stator to prevent right-hand rotation of the tubing string within the well casing so as to enable operation of the progressive cavity pump.
Within a wellbore, it is often desired that in addition to enabling the operation of the progressive cavity pump, that one or more lengths of coiled tubing and/or cabling also be run within the wellbore to regions below the pump for various purposes such as to deliver hot oil or diluent to break up sand or heavy oil within the formation and/or to communicate with one or more instruments beneath the progressive cavity pump. That is, as operators seek to collect more information from a well during production and/or seek to concurrently perform other operations within the well using additional systems, auxiliary lengths of coiled tubing or cable may be run past the torque anchor.
In addition, in deviated wells in particular, it is desirable to maintain the progressive cavity pump in a centralized position to enable coiled tubing and/or cable to be readily run past the progressive cavity pump without binding or wedging of this auxiliary tubing or cabling between the torque anchor and casing or wellbore.
As a result, there has been a need for a torque anchor that, in addition to performing as an effective torque anchor, improves the ability of the operator to perform other operations within the well. Further, as progressive cavity pumps are often used in wells containing sand or other heavy substances it is desirable for the torque anchor to utilize a housing with as much flow-through space as possible, achievable by utilizing a housing with a smaller diameter and relatively larger slips.
A review of the prior art indicates that a number of different anti-rotation systems have been developed in the past that utilize a variety of concepts to provide different functionalities to an anti-rotation system or torque anchor.
For example, Advantage Products Inc. (Calgary, Alberta) produces a torque anchor that utilizes a single pivotable slip for deployment against well casing. In this system, the single slip extends from the main body of the torque anchor upon clockwise rotation of the tubing string such that when the slip engages with the well casing, the main body of the torque anchor is forced to move across the casing to the opposite side of the casing. This system can provide a pinch point that can damage tubing running adjacent to the torque anchor. In addition, this system by virtue of the main body of the torque anchor engaging with the well casing will similarly cause tools such as the stator of a PC pump to be biased against the well casing causing extra wear on such tools.
Canadian Patent 2,159,659 and U.S. Pat. No. 5,636,690 describe a torque anchor having pivotable slips for engagement with the well casing. In a horizontal and some deviated operations which make up a significant portion of all applications, a single slip engages and the main body of the torque anchor is pressed against the opposite side of the casing to the engaged slip.
Canadian Patent 2,220,392 describes a torque anchor having a plurality of drag slips that emerge from a slip cage and do not define a fixed volume of space between the slips.
Canadian Patent 2,238,910 describes a torque anchor to prevent right-hand rotation of tubing string within a stationary well casing. The system includes a fixed slip, two floating slips and a means for rotating the slips about the housing to create varying diameters of overall tool.
Canadian Patent 1,274,470 describes a no-turn tool having three movable slips that do not define a fixed volume between the slips.
Otatco Inc. (Calgary, Alberta) produces a torque anchor having a one piece body with integral slips and a collar to prevent right-hand rotation of a tubing string within a stationary well casing. The system includes a no-spring system having collars mounting passive dogs that provide anti-rotation when the collars are counter-rotated with respect to one another.